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There are various:
easytag has a lot of options
kid3 if you're on a Qt/KDE environment
id3v2 or eyeD3 for the command line
Generally music players can also edit common tags, f.e. banshee, rhythmbox or amarok
and a lot others, try searching your distributions repository and test some of them.

A nice alternative is SmartGit. It has some very similar features to SourceTree and has built in 3-column conflict resoluvtion, visual logs, pulling, pushing, merging, syncing, tagging and all things git :)

If you are willing to go outside your comfort zone, LaTeX Beamer is really the only thing I have found that can match Keynote's output for Linux.
Ease of use is a problem with LaTeX though, look at LyX for a nice editor, and some examples.

There are many text web browsers, as there are many graphical web browsers, so it really depends on what you're looking for. lynx is a common slim choice, Elinks has many features. Both of these support other protocols, such as ftp and gopher (Elinks even supports bittorrent). Elinks may also be built with support for JavaScript, using Mozilla's former ...

The first place to look is your distribution's package list. That's where you'll find the easiest-to-install programs. Some package management tools provide advanced ways of searching it.
On Debian and Debian-based distributions (e.g. Ubuntu), you can search package descriptions with apt-cache search or aptitude search (on the command line), or through the ...

There are a number of tools that are usable:
meld
kompare -- diff file viewer
kdiff3 -- file difference viewer
Diffuse -- file difference viewer
Do you have two files and want to view their differences? Use a "file difference viewer". Do you have a diff file and want to look at it in an easy-to-read display? Use a "diff file viewer".

Personally, i3 takes the best features of the other big tiling-wm's (Xmonad, Awesome, DWM, etc) and combines it into one, Combined with dmenu/conky/dzen2 it's just what I look for in a WM. Check out the page; http://i3.zekjur.net/

There are several choices of minimal, relay-only mail transfer agents (MTAs, or "mail servers"), some of which have been mentioned in other answers:
msmtp http://msmtp.sourceforge.net/
nullmailer http://untroubled.org/nullmailer/ (my personal favourite)
esmtp http://esmtp.sourceforge.net/ (unmaintained)
sSMTP http://packages.debian.org/source/sid/ssmtp (no ...

I use pdftk mainly. But here are some others to consider:
pdfsam (PDF Split and Merge): "pdfsam is an open source tool (GPL license) designed to handle pdf files"
PDFJam "A small collection of shell scripts which provide a simple interface to much of the functionality of the excellent pdfpages PDF file package (by Andreas Matthias) for pdfLaTeX." (You can ...

"Complicated to configure" varies greatly depending on what languages you're proficient in. XMonad was extraordinarily complicated for me to configure, but that was because I know absolutely no Haskell, and that's the language the configurations are in.
The two tiling window managers I've used and quite liked are:
Awesome. Awesome configurations are in ...

I think you are referring to removing the caret-M at the end of lines. You can use search and replace in vi to do this.
In vi I normally do: (where "^" represents CTRL):
:%s/^V^M//g
Which shows on the screen as:
:%s/^M//g

SQLite's small size and levels of completeness, stability & speed make it a popular choice for low-resource environments, which embedded systems usually are. It is used by parts of the current iPhone, Android and Symbian phone operating systems for this reason.
You might want to add some details to your question to get more specific answers: do you know ...

Inkscape is today the de facto standard. In earlier times, people used xfig and I still love it, however it isn't for the faint of heart as the user interface is disturbingly ugly and unusual (but highly efficient once you got to know it). Then there is also dia which is modeled a bit after xfig but with a normal Gtk GUI.

From what I found there is only ongoing development in links project (i.e. no releases). Here's more:
w3m - last sources from january 2011, previous from 2007 and 2004. Some major development was done in 2003 and 2004.
elinks - "The current unstable version is 0.12pre5, released on 2009-07-08.
The latest stable version is 0.11.7, released on 2009-08-22."
...

There's a Arch Linux wiki entry comparing 13 different Tiling Window Managers, in grid-like fashion, here on the Arch Linux Wiki. Perhaps it would be hepful.
I haven't tried any of them yet, personally, but plan to in the near future when I have some time, so I'm following this thread closely as well.

I know two programs for manipulating PDFs under Linux:
PDEedit "Pdf Editor is primary created for simple editation and manipulation with objects of documents in PDF format and storing them as new version of document. Editation and manipulation with objets is by graphical and by commandline interface too. For simple use command line is using script language, ...

For commandline IRC, the most popular or commonly-used one is probably irssi. It's very robust, very flexible, highly extensible with scripts and layout themes, very well-documented, and has a decent community of users and supporters.

ImageMagick comes with the import utility to take screenshots. It has tons of options, but by default it lets you draw a rectangle on the screen and saves just that portion. If you want an entire window you can use -window ID; the identifier "root" captures the entire screen

I use conky to display date, battery, cpu, ram and swap information. You can find my conky file here or take a look at a thread about conky configs in the arch-linux forum. There you find many different configs and screenshots of conky in use.

I'd like to recommend two different tiling window managers, one dynamic and one manual.
XMonad is very powerful yet easy to learn, there is a short guided tour that explains its basic features and key bindings. It integrates smoothly with GNOME, the documentation is comprehensive and there are lots of additional extensions available. It supports the ...

R is better at this sort of thing because:
It's a complete programming environment, with C and Fortran-compatible extension APIs, so there is literally nothing you can't make it do.
Many have already contributed their solutions to common problems to the CRAN: Comprehensive R Archive Network.
There are many books on time series analysis and R in general.
...

Sounds like a job for Perl with Text::CSV.
perl -MText::CSV -pe '
BEGIN {$csv = Text::CSV->new();}
$csv->parse($_) or die;
@fields = $csv->fields();
print @fields[1,3];
'
See the documentation for how to handle column names. The separator and quoting style can be tuned with parameters to new. See also Text::CSV::Separator for ...